Vibration diagnosis

[malum]

I'm going to assume that this isn't a model specific problem and post it here but for the record it's a 2002 A4 3.0 V6 petrol convertible, multitronic auto.

I have a vibration that comes in at 17-18mph and goes away at 35ish but is at its worst at 20mph I can feel it through the steering wheel and the seat. It's quite subtle. It's there on acceleration and braking, sometimes it worse on braking, sometimes it's not there at all on braking. Still happens if I flip it into neutral.

I took it in to my local Audi specialist they checked all suspension bushes etc. and they were fine They found play in one of the CV joints which they duly changed, but this didn't fix the problem.
They didn't have time for further diagnostics so I took it away but the mechanic thought it might be a catalytic converter blocked up based on a slight whistle he could hear from the exhaust in that area. The theory being that blow back into the engine would cause the vibration. This doesn't make much sense to me as it would surely be worse at higher revs/speed and would affect the performance (which is just fine).

They didn't check the wheel alignment but I'm assured that bad alignment would not cause vibration.
I swapped the wheels front and back as they needed swapping anyway and it feels no different. (I would expect it to feel different if I had a buckled wheel and swapped front and back) Visual inspection of the wheels shows no damage and the tyres are all recent (they are always recent due to the rate it goes through front tyres!)


Before I go down the route of expensive diagnostics for the catalytic converter does anyone have any thoughts?

TIA

 

[Liquidfusion-S3]

http://www.audi-sport.net/vb/audi-s4-a4-a4-cab-b8-chassis/211211-rumble-low-speeds.html

 

[malum]

Thanks
Mine isn't a noise (it's whisper quite) just a vibration/juddering.
Wheel balance seems unlikely at that speed plus the swapped wheels would have made a difference to where the vibration was felt.

 

[Spartan117]

Malum, I have a 2007 B7 2.0 tfsi Cab and I also notice a faint rumble at around the same speed, especially when I turn right. I cannot hear it but feel it through the brake and accelerator pedals at around 17-25 mph. It's still there when in neutral. I think that it's either wheel bearing or CV joint. I personally think it's wheel bearing as the alloy on the front left had a large gouge in it when I bought the car. Also, when it drove it home after my purchase, there was a bad vibration at around 70. This has nearly gone with the replacement of the wheels but there still is a slight vibration at 80 mph ( where conditions allow) which sort of rules out CV joint as the car is on a straight bit of road by then. So my money is on wheel bearing.
Give it a go and let me know.

 

[malum]

Thanks
Yours sounds like a bearing and a wheel balance issue
I'm pretty sure mine isn't a bearing as there is no noise and absolutley no play in any wheel.
I don't have a rumble just vibrarion/judder

 

[Nilz]

Could it be the tyres??

I remember I had a set of Good Year Eagle F1s on my car a few years ago and the noise they made was exactly like the wheel bearing noise, checked them and everything else and it was fine, turned out it was the tyres and it was heavily documented on the net too.

Another thing I remember reading from a while back was someone on here had there tyres fitted and they had water in them, this was causing a bad rumbling noise too.

 

[malum]

Could it be the tyres??
Another thing I remember reading from a while back was someone on here had there tyres fitted and they had water in them, this was causing a bad rumbling noise too.

OK: Let's be clear: There is no noise!! just vibration/judder bewteen 17mph and 35ish Mph

 

[Nilz]

OK so theres no noise??

Have you checked the wheels are all balanced up properly, I know its at a low speed and you have swapped the wheels over, but for the sake of a 10 min job and probably a fiver, its worth a try isnt it??

 

[malum]

OK so theres no noise??

Have you checked the wheels are all balanced up properly, I know its at a low speed and you have swapped the wheels over, but for the sake of a 10 min job and probably a fiver, its worth a try isnt it??

Not yet. It's on my list of things to do next (along with wheel alignment) but balance seems very unlikely at 20mph.
Before I take it in again I want as many ideas as possible about what it could be. I will elieminate the cheaper ones first

 

[Spartan117]

Malum,
my car has the same, no noise but vibration/judder between 20 and 35 mph, felt through the brake and accelerator pedals and roundabouts.

 

[malum]

Well diagnosis just became a lot easier. The gearbox has packed up. No drive either forwards or backwards. Explains the juddering
Ho Hum

 

[Nilz]

Oh man!!!

 

[malum]

Oh man!!!

Indeed!

It's borderline but I've decided to have it fixed (my gearbox rebuilt) the car has only done 57,000 miles and has been cared for in an expense is no object manner for the last three years (my ownership) so the rest of it is in great condition.


I had the gearbox oil changed at the specified intervals but I did have an issue with it last year where it blew a pipe off the gearbox and dropped all its gearbox oil out (disgraced itself on Bond Street :lol) So I drove it for a while with no oil in it (couple of miles). Pipe was was repaired and all was fine (or seemed to be) but it must have been damaged.


There is a specialist gearbox place quite nearby. I will report back on how it goes.
£2,500 inc VAT, in case anyone has the same problem and needs a figure! with 12 month warranty. Includes upgraded clutch pack and remapped software.